Pre-heat oven to 400F (200C), grease and flour or line muffin tin with paper liners (this recipe makes 9 muffins).
TOPPING
In a small bowl combine the sugar and flour cut in the butter until the mixture resembles large crumbs, then stir in the chips, set aside.
MUFFINS
In large bowl whisk together the flour, sugar, baking soda, baking powder and salt, then add mini chocolate chips, stirring gently to combine.
In a medium bowl whisk together the egg, yogurt, milk, vanilla and oil until combined.
Pour wet mixture into dry mixture and stir just until combined (stir approximately 15-16 times no more). Batter should be lumpy.
Fill the muffin tins almost to the top. Sprinkle with the topping. Bake for 5 minutes then lower the heat to 350F (180C), continue to bake for approximately 12-15 minutes, check for doneness with a toothpick. Let cool for about 5 minutes in the pan then move to a wire rack to cool completely. Enjoy!
Notes
For room temperature ingredients remove from the fridge 30-45 minutes before using.I used a 6 medium size muffin tin but you could double the recipe and make 6 jumbo muffins.Let the muffins cool completely then store in an airtight container or bag, store them at room temperature. Muffins should last up to 2-3 days or 7 days in the fridge.Freshly baked cooled muffins can also be stored in the freezer, be sure to place in an air tight container or freezer bag. They will keep up to 3 months.